Year	million ton-km
1970	1
1971	1.6000000238
1972	2.2999999523
1973	1.8999999762
1974	5.0999999046
1975	7.4000000954
1976	8.8000001907
1977	9.3999996185
1978	13.1000003815
1979	12.6999998093
1980	16.2000007629
1981	17
1982	12.8999996185
1983	9.3000001907
1984	11.3000001907
1985	15.6999998093
1986	12.5
1987	13.5
1988	9.3999996185
1989	10
1990	17.7000007629
1991	15.3999996185
1992	12.5
1993	9.5
1994	12.6000003815
1995	16
1996	16.2000007629
1997	15.6000003815
1998	13.3000001907
1999	18
2000	20.813
2001	20.813
2002	13.178
2003	16.054
2004	19.748
2005	22.118
2006	16.385
2007	17.532
2008	14.290000000000001
2009	11.433
2010	4.6709182
2011	6.46072795302386
2012	4.66339165780686
2013	1.517388
2014	1.517388
2015	0.0280427875669882
2016	0.028381977
2017	0.025670514
2018	0.0256386216924769
2019	0.024356690607853
2020	1.782252
2021	3.137035